<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            text-align: center;
        }

        .ad-left {
            position: fixed;
            top: 300px;
            left: 0;
        }

        .ad-right {
            position: fixed;
            top: 300px;
            right: 0;
        }
    </style>
</head>

<body>
    <div class="box">
        <img src="img/box.png" alt="">
    </div>

    <div class="ad-left">
        <img src="img/ad-l.png" alt="">
    </div>
    <div class="ad-right">
        <img src="img/ad-r.png" alt="">
    </div>

</body>

</html>